Because of abuses
One of the public forces that drove govt to "ban" Anabolic steroids
was high-profile athletes, some of who 'professed' never to have used them, were proven to be 'guilty'.
Soit was 'secret', 'illicit' +not above board. Much use was 'amateur' and not managed by competent physicians. Doctors in general were either negative, uninformed of legitimate usage, or both. The media had a profit heyday.